A variety of optical inspection systems for examining objects are known. A typical system of this type includes means for establishing, in an image plane, an image of an object to be examined. An array of photocells is placed in the image plane at the shadow boundary of the image. In one such prior art system, signals corresponding to the output generated by the photocell array during each interval of an inspection sequence (representative of the dimensions of the object measured) are compared with signals stored in a standard register to provide a digital readout which represents the deviation of the object from the standard. In an alternative system, the signal from each cell, during each such interval, is applied to electric circuitry which compares the value of the signals with preselected signals of fixed limits and furnishes accept or reject decisions to a memory.
Prior art systems of this type require the storage of signals which represent the standard of comparison with which the signals, provided during each interval, are compared. These systems operate by storing and comparing the output signals generated during each interval in the inspection sequence, an operation which consumes a considerable amount of computer memory and processing time. Further, such systems typically require the rotation of an object about its axis of symmetry for a full inspection sequence.